A variety of products having, for example, a magnetic structure, an optical structure, and a structure including a semiconductor memory, are commonly used as media and apparatuses for recording and playing back information. Particularly, magnetic-tape recording/playback apparatuses using magnetic-tape media for magnetic recording have a history of many years and wide performance and they are considered to continuously have an important role in future years.
The magnetic-tape recording/playback apparatuses are characterized in that the performance thereof is evaluated dependently on the performance of recording media (magnetic-tape media) and also characterized in that they adopt a structure giving synchronous operation. The magnetic-tape media are widely used as media involved in sequential recording and have a reputation in a broad range of applications due to the following:    (1) inexpensive bit cost    (2) a vast amount of bit capacity per roll    (3) high manageability owing to the removable media and the capability of managing them for every roll    (4) use for archives with a function of storing records for a long time.
Especially, the recording performance of the magnetic recording media depends on the coercive force and the chronological deterioration of the coercive force is determined from arrhenius plot. The chronological performance of the magnetic recording media is evaluated based on an inclination represented in a semilogarithmic scale. In the present circumstances, the function of storing records for a long time continues to improve along with the improvement and development of magnetic materials.
Meanwhile, a mechanism for reading and writing information based on the variation in magnetic flux density during a relative movement with respect to the head of a magnetic tape synchronously transfers the information to other apparatuses and devices. Hence, this mechanism is appropriate for direct information transfer that is synchronous with the other apparatuses and devices through, for example, a dedicated transmission path. Accordingly, known video tape recorders (hereinafter referred to as VTRS) and video cassette recorders (hereinafter referred to as VCRs), which are typical synchronous magnetic-tape recording/playback apparatuses, have been embodied separately or as complements or backups for random-access recording/playback apparatuses on the assumption of use of the dedicated transmission path.
As described above, in the known VTRs, which are referred to as linear devices, images and voices are all synchronously input and output. Hence, the playback operation of tape media at a sending VTR must be simultaneously and synchronously performed with the recording operation at a distributed server at a certain rate in a real time environment in order to copy the contents recorded on the tape medium from the VTR to the server or the like. For this reason, for example, the synchronous VTRs cannot play back video and voice data corresponding to five minutes over a time period of 30 minutes and they are not appropriate for recording the video and voice data corresponding to five minutes input over a time period of 30 minutes.
In order to control each device that transfers information under strict time management and to make the device follow the time restriction, the synchronous VTRs need to independently transmit video and voice data, time codes, control signals, and so on. The synchronous VTRs also need to change the connection or separately provide reverse connection for reversing the sending VTR and the distributed server, thus complicating the operation and disadvantageously increasing the production cost.
Application of a network environment, such as Ethernet (trademark), which is a typical local area network (LAN), is desirable for simplifying, for example, unifying the connection. However, there are some bottlenecks and problems to be resolved to connect the known synchronous VTRs as nodes to the communication network.
First, synchronous transmission of the time codes, the control signals, and delivery content through the communication network shared by a plurality of nodes is not assured, unlike the transmission through a dedicated transmission path, and asynchronous transmission of them prevails. Hence, the known synchronous VTRs are not accommodated to the transmission of the time codes, the control signals, and the delivery content.
Transmission of playback information from the synchronous VTRs or receipt of recording information therein by using a dedicated transmission path or a private communication network having an assured transmission rate does not produce problems with the recording or playback quality because of an assured fixed transmission rate. In contrast, the transmission rate of a network line shared by a plurality of nodes varies more than that of the dedicated transmission path and varies dependently on the amount of traffic at that time. Such dependency on the state of the line possibly creates problems with the quality and the like of the transmission information. For example, on the physical layer where the transmission rate cannot be maintained at a certain value due to the variation in traffic on, for example, the Ethernet (trademark), it is possible that data on the magnetic tape cannot be smoothly transmitted and received.
Additionally, the known synchronous VTRs are not appropriate for sequentially transmitting two scenes recorded on separate positions on a magnetic tape.
Furthermore, since other jobs are paused while one job is being processed in the known synchronous VTRs, there is a problem in that it takes a long time to complete all of the jobs.